Risk Factors CHE Venous stasis Malignancy Prior dvt obesity ·Age>70 ° Estrogen/OCP ° Prolonged Bed Rest ° Pregnancy(esp3 Immobilization months post partum) Surgery requiring Lower ext injury 30 minutes general Previous anesthesia thrombophlebitis Orthopedic surgery Coagulopathy Stroke MBBS project, Zhongshan HospitalMBBS project, Zhongshan Hospital Risk Factors • CHF • Malignancy • Obesity • Estrogen/OCP • Pregnancy (esp 3 months post partum) • Lower ext injury • Previous thrombophlebitis • Coagulopathy • Venous Stasis • Prior DVT • Age > 70 • Prolonged Bed Rest • Immobilization • Surgery requiring > 30 minutes general anesthesia • Orthopedic Surgery • Stroke